Maintenance-free batteries have been known for some time. The term "maintenance-free" denotes a battery in which there is no need for the addition of water throughout the useful life of the battery. Thus, venting systems for maintenance-free batteries do not require the removal of the vent system for access to each cell. Because of the diversity of applications, however, low maintenance batteries (requiring minimal periodic addition of water) are still widely in use, and are well known for reliability under a wide range of conditions of abusive over-discharge, temperature variations, etc.
In all cases, the vent system must provide the absolute minimum loss of electrolyte under a wide range of conditions to enhance the life and operation of the battery. Even during the normal operation of a battery, water is electrolyzed into hydrogen and oxygen while temperature excursions produce water vapor, both of which will tend to be lost through the venting system. A well designed vent network must prevent this loss by capturing, condensing and draining all fluids back into the cells. A battery designed for starting, lighting, and ignition (SLI) will experience a variety of rough handling during its manufacture, storage and distribution including an occasional accidental tilting of the battery on its side, a variety of angled inclines once the battery is in vehicle, as well as normal vibrations. A well designed vent system must prevent or minimize spilling, and also safeguard the battery against external ignition sources.
Traditionally, vents have been designed for the most common location of vent ports, i.e., centered on the battery cover. Gang vents designed to fit on batteries of this design seldom experience pressurized electrolyte reaching the openings on each gang vent barrel while tilting, e.g., 45% to either side (as opposed to either end) of the battery. Recently, however, requirements to move the cell ports asymmetrically on the battery casing has demanded a different approach to the vent design.
Where the cell ports are located relatively close to one side of the top wall of the battery casing, tilting of the battery in a direction toward that one side may force liquid up into one or more vent barrels, amplified by the internal positive pressure of gases generated during charging. Tilting of the battery toward the opposite side, however, will not result in a loss of electrolyte since the acid level will remain below the cell port or vent orifices. This invention relates to a unique vent system which will prevent the loss of electrolyte even when the battery is temporarily tilted completely onto the side closest the vent ports and with the acid level above the vent orifices.
Thus, in accordance with an exemplary embodiment of the invention, flooding and spewing of electrolyte through the vents is prevented by utilizing the internal pressure of the electrolyte against the underside of the vents to prevent flooding, while any significant amount of fluid that may have entered into the vents will be contained and later quickly drained back into the cells, once the battery is set upright. This is accomplished by making the vent barrels (three, in the exemplary embodiment) slightly different in internal cross section, such that electrolyte enters through the outer barrels first. This arrangement allows a minute amount of electrolyte into the outer chambers of the vent cap which will quickly produce air pressure which is transmitted into the center chamber causing the fluids to become air locked, thus preventing the ingestion of additional liquid and stopping the further flow of electrolyte toward the vent frit area.
Additional improvements have been incorporated by speeding the drainage of ingested fluids back into the cells by providing sloped surfaces inside the vent cap insert, and designing barrel drippers to protrude below the barrel line. This is significant in that liquid that "hangs" in the barrel area can otherwise be pushed upwards by the gases generated during charging.
In accordance with its broader aspects, the present invention relates to a multiple vent plug assembly for a corresponding number of vent ports in a vehicle electrical storage battery, the vent plug assembly comprising a gang vent insert formed with three chambers, each chamber having substantially aligned vent barrels and associated drain holes; a frit area enclosing porous frit material, the frit area open to atmosphere; an overcap secured to said gang vent insert; and means provided in the gang vent insert and the overcap for creating an air lock within the multiple vent plug assembly and for thus preventing spillage of battery electrolyte to atmosphere through the frit area.
In another aspect, the invention relates to a multiple vent plug assembly for vent ports of an electrical storage battery, the assembly comprising a gang vent insert having a base wall and an upstanding peripheral rim defining a pair of side walls and a pair of end walls; an overcap including an inner rib adapted for engagement with said upstanding peripheral rim of the gang vent insert; the insert including first and second parallel partitions extending between the pair of side walls to thereby divide the insert into three vent chambers including end chambers on either side of a center chamber, each chamber having a hollow vent barrel extending downwardly from said base wall and terminating at a drain hole; third and fourth partitions extending partially between the pair of side walls and a fifth partition extending between and perpendicular to the third and fourth partitions to create, in cooperation with a portion of one of the side walls, a frit area for supporting a flame arrestor comprising a glass frit composition; the frit area having a slot therein which, when the assembly is in place on the storage battery, opens to atmosphere; and wherein the first, second, third and fourth partitions are formed with passageway openings arranged to permit air at atmospheric pressure to enter the center chamber from the end chambers and from the frit area, to thereby create an air lock preventing battery electrolyte from escaping through the drain holes and the frit area vent aperture in the event the battery is tilted to a position where battery electrolyte is at a level above the battery vent ports.
In still another aspect, the invention relates to a gang vent insert for a multiple vent plug assembly utilized to cover a plurality of vent ports in a vehicle electrical storage battery cover, the gang vent insert comprising a substantially rectangular member having a base and an upstanding peripheral edge including a pair of opposed side edges and a pair of opposed end edges, and a pair of laterally spaced first and second partitions extending between said opposite side edges of the upstanding peripheral edge to thereby divide the insert into three chambers including a pair of end chambers on either side of a center chamber; each chamber provided with a substantially cylindrical vent barrel extending downwardly from the base, the vent barrel including a funnel portion terminating at a drain hole, the drain holes in the end chambers having first diameters larger than a second diameter of the drain hole in the center chamber, all of the drain holes having a common centerline extending perpendicular to the laterally spaced first and second partitions; and wherein each of the first and second partitions is formed with a notch located on the other side of the centerline, and offset from the drain holes.
The details of the invention will become apparent from the description which follows.